Remisiewicz M., Tree A.J., Underhill L.G. & Nowakowski J.K. (2014) Geographical patterns in primary moult and body mass of Greenshank Tringa nebularia in southern Africa. ARDEA 102 (1): 31-46

Greenshanks Tringa nebularia show various patterns of primary moult in the northern hemisphere, but farther south moult patterns are known only fragmentarily. We identified geographical patterns in primary moult and pre-migratory fattening of Greenshanks on their southernmost African non-breeding grounds. We compared primary moult (using Underhill-Zucchini models) and body mass at a population level based on 356 Greenshanks caught in 1968–1998 at inland wetlands in Zimbabwe, and on the east and west coasts of South Africa. About 20% of immatures replaced one to five outer primaries in December–May, a rare pattern in the north. Sub-adults moulted all primaries on average 40 days earlier than adults, yet at the same rate. Adults started primary moult on average 16–19 days earlier in Zimbabwe and at the east coast than at the west coast (7, 4, 23 September, resp.). These dates correspond with the Greenshanks’ broad-front arrival in Zimbabwe and the east coast, and their later arrival at the west coast. Moult took 10–17 days longer on average in Zimbabwe and at the east coast than at the west coast (122, 115, 105 days, resp.), thus the end of moult coincided within six days (31 December–6 January). Pre-migratory fattening began about 13–19 January across all regions. The mean departure fat loads of adults were 76 g in Zimbabwe, 116 g at the west coast and 125 g at the east coast. The heaviest adults from all three regions could reach the Nile Valley or the Red Sea coast in one non-stop flight. We suggest that Greenshanks at inland wetlands of Zimbabwe benefit from a shorter return migration distance and lower competition than at the coasts, and abundant food during the entire austral summer in favourable years, but can move on to the coasts if conditions deteriorate.